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Old 01-02-2008, 11:02 PM   #1
williaty
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Default Why Is The Engine Knocking Like Mad During Cold Snap?

OK, so we got hit by a cold snap today, about 20F colder than I've ever logged the car. I actually recorded an IAT of 5F as I started up the car! For some reason, the car was knocking LIKE MAD today. Very, very frequent knock and HUGE corrections (like 5-7 degrees FLKC+FBKC). Once the car got hot enough than the under-hood temps pushed the IATs up into the 60s (about 30 minutes of driving), the knock dropped back down to about what I've been seeing lately.

What gives?

At first I thought maybe the colder air was dense enough to raise my load (increased load->increased knock), but once I looked at the data again, it's was having a fit even at part-throttle where the loads were no higher than I had been seeing (~0.6-0.8g/rev). What the heck was going on while it was so cold?
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Old 01-02-2008, 11:12 PM   #2
NYSTI
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Quote:
Originally Posted by williaty View Post
OK, so we got hit by a cold snap today, about 20F colder than I've ever logged the car. I actually recorded an IAT of 5F as I started up the car! For some reason, the car was knocking LIKE MAD today. Very, very frequent knock and HUGE corrections (like 5-7 degrees FLKC+FBKC). Once the car got hot enough than the under-hood temps pushed the IATs up into the 60s (about 30 minutes of driving), the knock dropped back down to about what I've been seeing lately.

What gives?

At first I thought maybe the colder air was dense enough to raise my load (increased load->increased knock), but once I looked at the data again, it's was having a fit even at part-throttle where the loads were no higher than I had been seeing (~0.6-0.8g/rev). What the heck was going on while it was so cold?


What kind of oil do you use?, & And when have you changed it? It is common for a slight knock in the Bloody cold, Thats why its good to use 0w30 or 0w40 In the Cold...
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Old 01-02-2008, 11:14 PM   #3
williaty
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5w30 Royal Purple, about 1k miles into the OCI.

Keep in mind, I'm not talking about a knocking sound, I'm talking about knock events as recorded by the ECU.
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Old 01-02-2008, 11:17 PM   #4
mickeyd2005
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Are you telling me that your IAT is 60F when ambient is 5F? Do you have some kind of short ram intake?

Your IAT should only be 5 to 10F higher than ambient.

Did you look at your total timing?

Take a look at ignition compensation by coolant temperature and ignition compensation by IAT.
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Old 01-02-2008, 11:19 PM   #5
NYSTI
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Plugs,Timming Belt?

Oh and if it gets colder~ do drop down in a 0w, Add life to your motor.
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Old 01-02-2008, 11:26 PM   #6
williaty
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The IATs, once the car is fully warmed, have never been lower than 30F above ambient. In fact, unlike the turbo cars, my IATs actually DROP during repeated 2k-redline WOT pulls. The stock RS intake pulls from inside the engine bay above the ABS thingy. It is most definitely a Hot Air Intake.

Though I wasn't logging coolant temp today, based on past experience, at the time I was getting the knock, the coolant temp would have been between 170 F and 195F.

If it's knocking at cold IATs, is changing the IAT temp compensation the correct way to fix it, or just a bandaid?

This is what the stock Timing Compensation (Intake Temp) table looks like:
Code:
IAT in Degrees Farenheit
-40	-22	-4	14	32	50	68	86	104	122	140	158	176	194	212	230
0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	-3.16	-3.87	-3.87	-3.87	-3.87	-3.87	-3.87
This is what the stock Timing Compensation A (Coolant Temp) looks like:
Code:
Coolant Temp in Degrees Farenheit
-40	-22	-4	14	32	50	68	86	104	122	140	158	176	194	212	230
15.12	15.12	15.12	9.84	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00
This is what the stock Timing Compensation B (Coolant Temp) looks like:
Code:
Coolant temp in Degrees Farenheit
-40	-22	-4	14	32	50	68	86	104	122	140	158	176	194	212	230
4.92	4.92	4.92	4.92	4.92	4.92	0.00	0.00	0.00	0.00	0.00	0.00	0.00	0.00	-1.05	-3.16
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Old 01-03-2008, 01:07 AM   #7
benw
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probably just an issue with cold internals. do you have an oil temp gauge? it takes 15-20 minutes for my oil to come up to full operating temps (90C). This is approximately 5 times longer than coolant temp! Most people mistake coolant temp to be operating temp, which is incorrect.
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Old 01-03-2008, 03:51 PM   #8
Wheeler Bement
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Default

I have the same issue. I find that my car has these little "transistions" where FLKC is going to happen and has to do with IAT, RPM, and Load. One day it will be good, the temps drop, it knocks, I advance the timing the knock goes away. IT warms up, and still no knock...go figure.

I am taking the path of advancement till no knock, and if it knocks when it gets warm, then I will start to mess with the compensation scaling. I have an EGT gauge and can get what I consider a fairly good representation of if I can go higher with advance.

something to consider.
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